Field of the Invention
The present invention relates to a feeding device, and more particularly, the present invention relates to a feeding device with multistage stop arms.
Description of Related Art
Conventional multi-function machines, such as a scanner, a copier, or other office machine with multi-functions, have an automatic feeding device (or named as automatic document feeder, ADF) for a user to add plural sheets without manual operation. FIG. 6 is a cross-sectional view of conventional feeding device. Referring to FIG. 6, a stack of plural sheets S are placed by a user, and then a sheet-separating roller A would be drive to rotate by the feeding device. The sheet-separating roller A and the friction roller B are acted jointly, and the plural sheets S are separated to feed into the downstream of the paper passage individually. Besides, in the automatic feeding device, the stopper C coordinated with the sheet-transporting roller D is usually applied to position the sheets for a user with convenience. As a result, when the feeding device practices the pick-up work, the situation of miss feed and skew resulted from sheet non-position will not be occurred.
However, in addition to the positioning function, the stopper needs to guide sheets in sequence preferably to ensure feeding smoothly, wherein the sheets are constituted a structure of wedge-shaped inclined plane for reducing the feeding error-ratio. The partial sheets located in lower layer of wedge-shaped inclined plane are close to the sheet-separating roller, and the partial sheets located in upper layer of wedge-shaped inclined plane are far from the sheet-separating roller. The above design can make the sheet-separating roller pick up the bottom sheets firstly. Otherwise, if the stack of the sheets can't be constituted the structure of wedge-shaped inclined plane, the sheet-separating roller would pick up the top sheets, and pick up the bottom sheets by friction simultaneously. This results in a feeding failure of the feeding device, such as multiple feeding, jamming, and sheet breakage. Therefore, making the stack of the sheets being the structure of wedge-shaped inclined plane by the stopper is important. But the difficulty is that: if the elastic force of the stopper is too light, the effect for guiding sheets in sequence can't be reached; if the elastic force of the stopper is too heavy, the thin sheet would not drive the stopper, and results in jamming. Therefore, how to design the elastic force of the stopper is an important issue.